AFAIK and if I understand your question, the memory allocated to this variable won't be 'trashed' if there remains reference of any kind to this memory block.
I mean as long as you got a reference to a variable (whatever the type hash,array,scalar) you will be able to access it via this reference...

my $ref;
{
my $foo=10;
$ref=\$foo;
print "foo=$foo\n";
print "ref=$ref ($$ref)\n";
}
print "foo=$foo\n";
print "ref=$ref ($$ref)\n";
[download]

will produce:

foo=10
ref=SCALAR(0x80f14ec) (10)
foo=
ref=SCALAR(0x80f14ec) (10)
[download]